Smokeless and odorless incinerator



Nov. 8, 1960 H. FRIEDBERG sMoxELEss AND oDoRLEss INCINERATOR I5Sheets-Sheet 1 Filed Aug. 21, 1957 IN VEN TOI?. HARRY Felt-Daems v BY W,@0, Z

A TTOENE'YS Nov. 8, 1960 H. FRIEDBERG 2,959,140

sMoKELEss AND onoRLEss INCINERATQR Filed Aug. 2l, 1957 5 Sheets-Sheet 2IN VEN TOR.

` /AEE Y FTQ/95526 BY l W, azu,

A 7 TORNEKS Nov. 8, 1960 H. FRIEDBERG sMoxELEss AND onoRLEss INCINERATQRFiled Aug. 21', 1951 s sheets-sheet s IN VEN TOR. Meer FAQ/05526 BY W,W7u,mff4

SMOKELESS AND ODORLESS IN CINERATOR Harry Friedberg, ICleveland, Ohio,assignor to Waste King Corporation, Los Angeles, Calif., a corporationof California Filed Aug. 21, 1957, Ser. No. 679,334

4 Claims. (Cl. 110-18) This invention -relates to improvements in asmokeless and odorless domestic incinerator.

One of the objects of the present invention is to combine in `a singledomestic lincinerator a number of elements and structures which havebeen previously kno'wn, together with some which are now as hereindisclosed, so that there is the smallest possi-ble offensive odor in theilue gases discharged into the atmosphere; smoke is eliminated; solidparticles are eliminated from the ilue gases; the temperatures developedin the incinerator are held so low that combustible surfaces, such asiloors and walls upon which or near which the incinerator is installedare not subjected to any form of lire hazard; and any garbage loadcharged into the incinerator is not subjected to the processes ofputrefaction but is efficiently reduced to ashes.

Another object of the present invention is to combine in a singledomestic incinerator a means for slowly dehydrating a moist charge inthe furnace chamber, a means for then igniting and burning the charge ata slow combustion rate so as to avoid overloading the discharge iluewith an excessive amount of products of combustion, Ian ash trap toeliminate particulate matter larger than fifty microns, and some matterbetween twenty-live and ifty microns, an after burner or secondarycombustion device for burning small particulate matter in the form ofaerosols traveling out `of the furnace chamber with the products ofcombustion, and a stack' dilution device which aids in the slowcombustion previously mentioned and which also aids in keeping thedischarge flue pipe to such a temperature that it is not a fire hazardt-o combustible iloors and Walls located near the incinerator.

Other objects include the arrangement of the parts to carry out thefunctions mentioned above, and further objects yand advantages of myinvention will be set forth in the accompanying description and clearlydefined in the appended claims.

In the drawings,

Fig. 1 is a vertical sectional view taken centrally through anembodiment of my invention and generally along the line 1--1 of Fig. 2;

Fig. 2 is a fragmental perspective View of a portion of the device ofFig. l with certain parts broken away and the ash trap moved out of itsoperative position in order to more clearly show the construction of theparts; while lFigs. 3, 4 and 5 are respectively a front elevationalview, a top plan view, and a side elevational View of the secondarycombustion device seen at the upper right hand portion of Figs. 1 and 2.

It has become evident for some time that awakened interest in airpollution problems would inevitably dictate that refuse incinerators beso designed that they would not contribute to the air pollution problem.I believe I am the iirst to combine in -a single incinerator all of thefeatures herein disclosed and so interrelated that a1- most anycombination `of domestic refuse can be consumed in the incinerator withpractically no air pollution rarice whatsoever. Each part of my devicecontributes to the eiliciency and functioning of the whole yand eachelement contributes to the unitary result.

Referring now to Figs. 1 and 2, a furnace chamber '10 is formed by meansof a front wall 11, side walls 12, a rear Wall 13 and a bottom wall 14.The front Wall includes an offset portion 11a for the accommodation ofan ash drawer 15, which may be removed for dumping through a suitableopening in the casing utilizing the handle 16. Practically, the furnaceand the ash pit are all a single chamber merely being separated by agrate 17 which may be reciprocated by means of handle 18 which is weldedto a bracket 19 which is in turn welded to the grate. A false rear Wall20 is provided for the furnace chamber 10, this wall being the frontlwall of an ash trap to be described later. There is a partial top wall21 covering the space between the side walls 12 and extendingsubstantially the distance between the walls 13 and 20 alreadydescribed. Other than this, the furnace chamber is open at the top asindicated at 22 for the introduction of material to lbe burned.

The ash trap comprises a front wall 20 mentioned previously on the sidetoward the furnace chamber, two generally parallel side walls 23 rigidwith the front wall and extending rigidly therefrom yand resting snuglyinside of the side Walls 12 of the furnace chamber sheets. The trap alsohas a bottom wall 24 which slopes from the front downwardly toward therear and stops short `of the rear wall 13 of the furnace chamber sectionso as to -allow material collected on the said bottom wall 24 to worktoward the rear and fall downwardly into the ash trap 15 deected by abaille member 25 secured to the rear wall 13.

Within the ash trap, impingement bafile plates are provided to catch thelarger particles which come over with the products of combustion, to`dissipate the kinetic energy of such particles, and thus permit them tofall substantially vertically downward in the ash trap. I-n the presentinstance, the ash trap is provided with a roof plate 26 rigidlyconnected to the front plate 20 and to the side plates 23 and slopingslightly downwardly toward the rear. A V-shape baille plate 27 extendingsubstantially vertical has upper tongues 27a less than the full width ofthe legs of the V-shape baille extending upwardly through suitableopenings in the roof plate 26, and tongues 27b at the lower end of asimilar character extending through suitable openings in the bottomplate 24. When the plates 24 and 26 are rigidly assembled in the ashtrap as shown in the drawings, the V-shape baille 27 is firmly held inthe position shown. Other baille plates 28, two being shown on each sideof the baille 27, are arranged generally parallel to the -arms of thebaille 27 and each baille plate spaced slightly rearwardly from theplate immediately forward of it, and overlapping at that point, so as-to provide llow openings 29 extending the full height of the baillesbetween the two adjacent bailles 28 on each side and between the baille28 and baille 27 on each side of the latter. The plates 28 are held inplace like the baille 27 by means of upper tongues 28a extending throughplate 26 and lower tongues 28b extending through plate 24.

Preferably, the ash trap is removably mounted in the furnace. In thedrawings, this is accomplished by providing two U-shaped seats 30, onesecured to each of the side walls 12 and adapted to receive the loweredge of plate 20 of the ash trap. This provides a simple pivotalmounting so that the ash trap may be swung from the operative positionof Fig. 1 to an inspection position of Fig. 2, or thereafter the ashtrap could be lifted out of place. It will be noted that most of theweight of the ash trap lies toward the right of the pivot seats30 as inFig. 1

and therefore this device willnorrnally return from the tilted positionof Fig. 2 to the operative position of Fig. 1. Two metal screws areshownat 31 which engage through sui-table openings 32 in an upstandingflange attached to the plate 20 and engage in other suitable openings 33in a flange connected with thetop plate 21 to securethe ash trap in itsoperative position. These are necessary when shipping the device butotherwise would not'be called for.

The ash trap above described substantially seals oft' the right handside of the furnace chamber as viewed in Fig. 1 save for an openingthrough which the products ofcombustion pass outwardly to the flue. Thisopening is' preferably covered with a coarse screen of hardware cloth orheavier rods as indicated at 34.

The flue pipe 35 is connected to the ue collar 36 in the customarymanner and is at the same level as the opening covered by the screen 34.At this same level, a secondary combustion device 37 is provided. Thisdevice preferablyconstructed of a suitable ceramic refractory materialso as to provide -a maze of material adapted to stand the hightemperatures encountered there and to give intimate contact betweenhighly heated surfaces and the unconsumed particles in the gases leavingthe furnace chamber 10, together with a supply of secondary air oroxygen so that all of these small particles are consumed in thesecondary combustion device and do not pass out through the ilue pipe35. The particular device 37 is clearly shown in Figs. 3, 4 and 5. Itconsists of a vertical back plate 38, a horizontal top plate 39, acentrally located vertically extending partition plate 40, and aplurality of arcuate plates 41 which pass through suitable openings inthe partition plate 40. The arrangement is such that the arcuate members41 act as balfles'so that the products of combustion cannot passstraight through the secondary combustion device but instead arediverted and come into contact with highly heated surfaces. lThesecondary combustion device is held in place by two bolts 43 whichattach the same to the plate 13.

Means is provided to slowly dry out any moisture in the material chargedinto the furnace chamber 10. Means is also provided for heating thesecondary combustion device 37 to a temperature preferably 1200 degreesFahrenheit or higher. My present invention combines these two functionsby the use of a combined burner shield and duct 44, preferably of castiron or the like, having a generally horizontal duct-like portion 44aconnected by suitable bolts to the front wall 11 of the furnace chamber.There is a registering opening through the front wall 11 which registerswith the hollow opening through the burner shield which is otherwisegenerally cylindrical in section and generally imperforate. The burnershield has a rearward generally vertically extending portion 44h whichextends upwardly and terminates just below the secondary combustiondevice 37. The parts are so arranged, as clearly seen in Fig. 1, thatmuch of the weight of the burner shield is held on the baffle member 25..Preferably, but not necessarily, the horizontal portion 44a of theburner shield is generallyi ovoid in section as clearly seen in Fig. 2with the arcuate end of smaller radius upwardly so that material doesnot readily lie on the top of the burner shield. Preferably also, butnot necessarily so, the vertically extending portion 44!) is graduallychanged to a rectangular section and ared outwardly as it extendsupwardly so that the terminal upper end is generally rectangular in formwith its longer dimension generally parallel to the plate 38 of thesecondary combustion de- Vice.

Means is provided for'heating the burner shield portion 44asubstantially continuously to a temperature below 400 degreesFahrenheit, the preferredl value being between 250 and 290 degreesFahrenheit. This is'the ideal tcmperature for this 4portion of theburner shield, in order to enableit to radiate that portion of theinfra-red spectrum which hasthe ygreatest ability to .penetrate the'charge inV the. furnace; In: vso doing, dehydration withoutcombus# tionof the charge is readily accomplished. Such dehydration, as is wellknown, stops bacterial action by the removal of moisture and tends "toeliminate the production of alcohols which otherwise would subsequentlybe oxidized to aldehydes. The aldehydes are major corporates producingoffensive odors vand have been blamed for the irritating nature of thesmog which is a plague in some of our major cities. The temperature ofthe horizontal burner shield portion 44a is such, due -to the constantlyapplied heat as to never rise high enough to ignite the charge in thefurnace chamber 10, or to cause the same to smolder. In the presentembodiment, this means for heating the horizontal portion 44a to thedehydration temperature is the small burner 45 which I have called themain burner because it operates all of the time. This burner is designedfor a uid fuel such as gas or oil. The form here shown burns gascontinuously and consumes 800 to 1000 yB.t.u. per hour of natural gas.'Ihis is somewhat less than one cubic foot of gas per hour.

Means is provided for heating the secondary combustion device 37preferably to a temperature of 1200 degrees Fahrenheit or higher so asto provide incandescent surfaces which will cause the combustion offinely divided particles otherwise passing out of the furnace chamber 10to the flue pipe 35. This could be a separate means, but I prefer tocombine it with the aforesaid burner shield and duct and have,therefore, bent the same upwardly to provide the vertical duct-likeportion 44h to carry combustion gases to a point directly beneath thesecondary combustion device. Atthe same time, it is desirableperiodically to ignite the dehydrated charge in the furnace chamber 10.i thus accomplish both of these purposes by providing a burner 46 ofgreater heating capacity than the burner 45 so that periodically theburner 46 may be ignited so as to raise the burner shield portion 44a toa temperature high enough to ignite the charge in the furnace chamberwhile the products of combustion of the burner 46 travel up the burnershield portion 44b to heat up the secondary combustion device to thedesired temperature. To accomplish this double purpose, the burner 4'6which I call the after burner, is provided with ya capacity of 20,000 to30,000 B.tu. per hour using natural gas. It will thus be noted that thefuel capacity of the burner 46 is between 20 and 40 times greater thanthat of the burner 45. This after burner 46 has many functions. Whenenergized, it heats the horizontal burner shield portion 44a to atemperature in excess of 800 degrees Fahrenheit which is more than ampleto ignite a charge in the furnace chamber 10 which is in contact withthe burner shield. Approximately 25 percent of the energy released bythe after burner is used up in igniting the charge. When burning, theafter burner aids in establishing and maintaining a proper andsatisfactory draft in the venting system connected with the Hue pipe 35.At an input of 20,000 B.t.u. per hou-r, the after burner sends up thechimney approximately 200 cubic feet of flue gases `and excess air perhour. This is a considerable amount and imparts a useful velocity to theiiue gases. The other function of'the after burner has been mentioned,namely, to superheat the products of combustion of a burning orsmoldering charge and bring the ceramic maze of the device 37 to atemperature at which catalysis can function. It is believed unnecessaryto describe the air and fuel supply to the burners 45 and 46 which areof a standard construction and supplied with the usual safety devices.The after burner 46 is actuated by a combination tirner` This could beprovided in several ways but l-as here shown,

atmospheric air is introduced as follows. Referring to the lower lefthand portion of Fig. 1, there is provided an opening 48 which allows airto enter, under stack draft pull, from the atmosphere to the spacebetween the furnace chamber walls and the surrounding casing. At thisparticular point, a bottom plate 49 provides the casing member nearestthe foor and a space is provided between this and plate 14. The enteringthen passes in the direction of the arrows of Fig. 1 between these twoplates and then upwardly on the outside of plate 13 and between thisplate and the rear wall of the surrounding casing. There is an opening50 through plate 13 at a suitable point along side the burner shieldportion 44b. Here, the cold air enters the ash trap and travels upwardlyalong side the hot burner shield 4411 (when burner 46 is operating) andthus the heated air passes over the ceramic maze of the device 37 duringthat time when the device 37 is being heated to a very high temperatureby burner 46. Thus, the gases from the furnace charge mix with thepreheated combustion air entering through the opening 50 and, because ofthe elevated temperature in the device 37, the extra oxygen and thecontact with the ceramic maze surfaces, the gases are caused to burn ina secondary combustion which burns the hydrocarbons to carbon dioxideand steam. It is interesting to note that the flue gases leaving thesecondary combustion device 37 are much hotter than when they enteredit.

.As mentioned previously, I use a barometric draft dilution device inorder to hold the combustion in the furnace chamber at a rate where theproducts of combustion can be handled and give a smokeless and odorlessincinerator. This device indicated generally at 51 in Fig. l is likethat shown and claimed in my copending application Serial No. 525,955,filed August 2, 1955, for Barometric Stack Dilution Device. The presentapplication covers the novel combination of this stack dilution deviceWith the secondary combustion dev-ice 37.

The stack dilution device includes a closed passageway 52 of rectangularsection which communicates at the upper end with the ue pipe 35 at avery short distance outsidethe vent collar 36 as clearly seen in Fig. l.At its lower end, the passageway 52 communicates with a box 53 of largercross section than the passageway 52. This box is completely closed savefor a slotted .opening 54 at the bottom side thereof. The arrangement issuch that air entering from the atmosphere through opening 54 must makethree right angle bends before it passesl out the ue 35. The passageways52 and 53 are of such a size as `to require a stack draft in excess of.025 inch to .030 inch (water gauge) to overcome the resistance of thepassageways 52 and 53. Experience has taught thatV at draft pressures of.030 or less, combustion in the incinerator chamber 10 is sufficientlyslow so that it is completed within the combustion chamber andpractically none takes place in the flue pipe. Since the averagechimney, under primed conditions, rarely has a draft in excess of .010inch of water gauge, there is no problem of excessive draft in thefurnace chamber 10 except at such time as the after burner 46 isenergized so that the large volume of products of combustion pass outthe ue 35 from the burner shield 44 as Vpreviously described. Theoperation of the stack dilution device 51 is such that when the draft atthe liue collar 36 passes .015 inch Water gauge, a very small amount ofair enters at the opening 54. At such time as the draft pressure in theue 35 increases, when the higher rates of combustion prevail afterburner 46 is lit, more and more air enters atthe opening 54 so that thedraft pressure at the flue collar 36 is held below .025 or .030. Atthese higher rates of combustion, the cold air owing through thepassages 53 and 52 enters the flue pipes 35, cooling the flue pipe andits gases over the ue length entirely, reducing the iiue pipe and gastemperature to a safe level. An additional arrangement which holds thetop of the ue pipe 35 to a safe temperature just outside the incineratoris the introduction of a false top 35a in the ue pipe exactly like thatshown at 35 in my above mentioned copending application, which servesthe double purpose of protecting the top of the flue pipe from directcontact with the hot gases passing through the main portion of the iluepipe and at the same time provides a space between the partition member35a and the top of the ue pipe so that air entering in the direction ofthe broken line arrows of Fig. 1 may travel directly through thispassageway ahd cool the top of the flue pipe at that point.

In the operation of my incinerator a compromise is necessary in that Ilimit the amount of air introduced into the combustion chamber 10. Thisis necessary in order to control the rate of combustion at a desiredlevel. If sufficient air for complete combustion were permitted to enterthe burning zone, combustion would be too rapid and the major portion ofthe burning gases would be found in the venting system, `giving rise tored hot iiue pipes and conditions hazardous to combustible material inclose proximity to the ue pipe. I, therefore, restrict the amount of airdelivered to the combustion chamber to slow down combustion, to obvia-teburning in the venting system. and to keep ue temperatures withinreasonable limits. This is accomplished by the stack dilution device 51.Too rapid combustion releases more flue gases than the average ventingsystem can handle. In devices not constructed according to my teachings,this evidence of too large a volume of ue gases is evidenced by outwardleakage around the charging door, seams, etc. A properly operatingincinerator has a neutral pressure zone some inchesbelow the chargingdoor. This is a fairly definitely marked plane, below which the liucgases are expanding and leak out of every possible opening, and abovethis neutral pressure zone air is sucked into the combustion chamber.This zone dictates the position of the vent collar 56. The charging`door is above this zone and air is sucked into the combustion chamberthrough the door seat. This charging door is indicated at 55 closing andopening just above the open top 22 of the furnace chamber 10. Thecharging door is pivoted to the casing at 56 and is provided with ahandle 57 for manual operation. Also, if desired, an ear 58 may beextended rearwardly rigid with the door 55 and there attached to a link59 which extends forwardly and downwardly to a point 60 where it ispivotally attached to a foot lever 61 which in turn is pivotally mountedon the frame or casing at 62.

Because I limit the rate of combustion in the chamber 10, for thereasons mentioned above, there are occasions when the amount of airentering the combustion chamber results in unburned gases reaching theflue system. This condition is corrected by utilizing the secondarycombustion device 37. The net result of this combination is that l burnthe combustibles in the chamber 10 at a controlled rate but neverthelessinsure that no unburned material, or substantially none, passes out theue pipe 35.

The function of the mounting of the ash trap on 'the hinge brackets 3i)is to facilitate access to the interior of the ash trap and access tothe secondary combustion device 37, by tilting the ash trap forwardly onits bottom pivots as illustrated in Fig. 2. It will be noted that thereis a recess 24a cut in the bottom plate 24 of the ash trap to lit aroundthe upstanding portion Mb of the burner shield. Also, there is a recess20a cut into the bottom edge of the plate 20 of the ash trap so as tolit over the burner shield portion 44a and this recess is large enoughto permit the tilting action shown in Fig. 2.

The operation of my incinerator should now be apparent. Material to beconsumed is placed in the furnace chamber 10 by opening the chargingdoor 55. The burner 45 preferably operates continuously and maintains atemperature below 400 degrees Fahrenheit in the lburner shield portion44a which slowly dehydrates any moisture in the charge. At periodictimes, the after burner 46 is turned on which increases the temperatureof the burner shield portion 44a to the ignition lpoint of the chargeand the hot gases `from burner 46 travel up the burner shield portion44]; heating the secondary combustion device 37 to incandescence. At thesame time, additional air entering through the opening 50 travels alongthe hot burner shield portion Mb so that it is preheated before reachingthe secondary combustion device to aid in additional combustion ofunburned products there. All this time, the stack dilution device S1 islimiting the amount of com.- bustion air drawn into the furnacechamberlll as previously described. The air for combustion entersthrough the opening 48 near the lower left hand corner of the drawing inFig. l and passes between plates 14 and 49 as previously described.There are other openings as indicated in plate ld and 63, and alsoalongside the side plates 12, where air may pass upwardly through apassageway between front wall 11 and the front wall of the casing, thispassageway being indicated at 64. Other air passes upwardly through thepassageway between rear plate 13 and the rear wall 65 of the surroundingcasing. This passageway is marked 66. The air passing up passageways 64and 66 and like passageways between the side walls i2 and the generallyparallel walls of the casing at those points, `all passes through theopen 'top 22 of the furnace chamber as shown by the curved arrows inFig. l. Thus, substantially all of the combustion air for the charge inthe furnace enters from the top. The amount of this air is restricted bythe stack dilution device 51 previously described. As the products ofcombustion pass out the opening inthe upper portion of wall 20 of theash trap and through the screen 34, the heavier particles impinge uponthe bafes 27 and 28 and drop downwardly into `the ash trap. Since thebulk of the air flow is across the top of the ash trap, the lowerportion thereof is very quiescent and the particles settle to the bottomof the ash trap and later fall into `the ash pit. The rest of theproducts of combustion pass through the secondary combustion device 37where the smaller particles are cornpletely consumed utilizing theexcess oxygen supplied by the air entering through the opening 50 aspreviously described. All of the products then pass out Ithe flue pipe3S which is further coo-led by additional air drawn through thepassageways 52 and 53. At the same time, the top of the Hue pipe at theexit from the incinerator is cooled by the air passing between theplates 35a and the top of the flue pipe. Thus, all of the factors whichI have described combine together to give a substantially completelysmokeless and odorless incinerator.

What is claimed is:

1. In a domestic incinerator, walls forming a furnace chamber open atthe top and having front and rear walls and two opposed side walls and abottom wall, a casing surrounding said chamber on all sides and spacedoutwardly therefrom, there being an opening in the upper end of saidcasing for the introduction of the charge to be consumed, there beingregistering openings through said furnace chamber rear wall and casingrear wall near the top of said rear wall and a hollow ue connectionextending through and engaging all sides of said registering openings, ahollow combined burner shield and duct extending from said front chamberwall horizontally through a lower portion of said chamber to a pointnear said rear chamber wall and then extending upwardly to a pointslightly below the level of said flue connection, an ash trap comprisinga front partition Wall extending approximately the entire distanceacross said chamber between said opposed side walls from the top thereofdown to a level below said burner shield and duct, said trap havingwalls extending rearwardly from said front partition wall, saidpartition wall being imperforate save for a through opening horizontallyopposite said llue connection, baille means supported in said trappermitting only non-linear gaseous llow through said baffle means, asecondary combustion device positioned at said flue connection near thetopof said upwardly extending burner shield and duct, and providing amaze of ceramic material able to withstand a temperature of at least1200 degrees Fahrenheit through which products of combustion must passfrom said' furnace chamber to said ilueconnection, there being a smallopening through said rear furnace wall adjacent said upwardly extendingportion of said burner shield and duct and communicating withthe'atmosphere for supplying combustion air to said secondary combustiondevice.

2. An incinerator comprising an outer casing, an inner casing within theouter casing, partitioning means in the inner casing forming on one sidethereof a combustion chamber and on the other side thereof a secondarycombustion zone and a ily-ash trapping zone, an exhaust ue communicatingwith the upper portion of said chamber and adapted to be connected to adraft source, ra secondary combustion catalyzer disposed in said zoneadjacent the junction between said due and said chamber and on thechamber side thereof, partition means near the exhaust side of saidcombustion chamber compelling products of combustion to leave saidchamber through an opening substantially horizontally opposite said ueand catalyzer, baille means betwen said opening and said catalyzerpreventing straight line ow of products of combustion therethrough, acombined burner shield and duct mounted inthe lower portion of saidouter casing extending horizontally partially therethrough and thenbending upwardly and terminating at a zone adjacent said catalyzer onthe chamber side of said partitioning means, means providing asupplemental source of oxygen to said catalyzer, a main and after burnerfluid fuel burner means in said outer casing and communicating with saidburner shield and duct at a point spaced from the upward bend of thesame, said main burner means having a capacity for heating said burnershield and duct to a temperature under 400 degrees Fahrenheit, saidafter burner means having a capacity for heating said burner shield andduct to a temperature over 800 degrees Fahrenheit, and a stack dilutiondevice providing communication between the atmosphere and said ueapproximately at the junction between said llue and said chamber holdingthe draft from said source under approximately 0.030 inch water gaugewhereby an induced flow of air from atmosphere through said device isthus operative to cool said flue during high rates of combustion in saidchamber.

3. An ineinerator comprising an outer casing, an inner casing within theouter casing, partitioning means in the inner casing forming on one sidethereof a combustion chamber and on the other side thereof a secondarycombustion zone and a fly-ash trapping zone, an exhaust ue communicatingwith the upper portion of said chamber and adapted to be connected to adraft source, a secondary combustion catalyzer disposed in said zoneadjacent the junction between said liuc and said chamber and on thechamber side thereof, partition means near the exhaust side of saidcombustion chamber compelling products of combustion to leave saidchamber through an opening substantially 4horizontally opposite saidiiue and catalyzer, ba-le means between said opening and said catalyzerpreventing straight line ow of products of combustion therethrough, acombined burner shield and duct mounted in the lower portion'of saidouter casing extending horizontally partially therethrough, 'ineansproviding a supplemental source of oxygen to said catalyzer, burnermeans for heating said combined shield and vduct only to a temperatureunder 400 degrees Fahrenheit, burner means for heating said catalyzer toapproximately 1200 degrees Fahrenheit, means for igniting a charge insaid chamber, and a stack dilution device providing communicationbetween the atmosphere and said flue approximately at the junctionbetween said ue and said charnber holding the draft from said sourceVunder approximately 0.030 inch water gauge whereby an induced-'flow ofair from atmosphere kthrough said device is thus oper ative to cool saidue during high rates of combustion in said-chamber.

4. The combination of claim 2 wherein said means providing asupplemental source of oxygen to said catalyzer comprises a passagewaycommunicating at one end with atmosphere and extending adjacently alongsaid upwardly bent portion of said burner shield and duct and 5communicating on its opposite end with said chamber.

References Cited in the le of this patent UNITED STATES PATENTS 964,568shannon July 19, 1910 10 10 Shannon Jan. 10, 1911 Cummings Mar. 10, 1925McKinley Aug. 6, 1935 Martin June 21, 1955 Hebert Aug. 23, 1955 Short etal July 3, 1956 Bratton Aug. 5, 1958 Triggs Aug. 19, 1958

